Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. On 6 May , Pfizer , which manufactures Viagra, told the Associated Press they will begin selling the drug directly to people on its site. This is likely to lead to dramatic price reductions. Keep from freezing. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection.Viagra dosage for erectile dysfunction (ED) is usually milligrams (mg), but those over 65 may start at 25 mg. Your doctor will also need to consider possible drug interactions. mg Typical dosages The following information describes commonly recommended dosages for ED. However, be sure to take the dosage your doctor prescribes for you. .  · For oral dosage forms (suspension or tablets): Adults—20 milligrams (mg) 3 times a day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 80 mg 3 times a day. Children 1 year of age and older weighing 45 kilograms (kg) or more—20 mg 3 times a day.